1. Field of the Invention
This invention relates to methods of and apparatus for controlling loads on an electrical power supply.
2. Prior Art
It is common practice for electric power to be supplied to consumers under a maximum demand tariff. In order to avoid the need for consumers physically checking and disconnecting loads in order to remain within an agreed maximum demand, it is possible, as is described in our U.S. patent application Ser. No. 121,203, filed Feb. 13, 1980 to provide means for automatically disconnecting a load circuit if the maximum demand is exceeded. For many consumers, particularly domestic consumers, it would be preferable to disconnect individual loads rather than to disconnect a complete circuit by switching means located at or near the position where the maximum demand can be monitored.
Techniques are known for the transmission of data between a utility and a consumer's premises by distorting the waveform of the supply at one point in the system and detecting the distorted waveform at a remote point; see for example U.K. Patent Specifications Nos. 1153908, 1168073 and 1341025.